Meltdown and Spectre CPU Flaws Affect Intel, ARM, AMD Processors

Unlike the initial reports suggested about Intel chips being vulnerable to some severe ‘memory leaking’ flaws, full technical details about the vulnerabilities have now been emerged, which revealed that almost every modern processor since 1995 is vulnerable to the issues.

Disclosed today by Google Project Zero, the vulnerabilities potentially impact all major CPUs, including those from AMD, ARM, and Intel—threatening almost all PCs, laptops, tablets, and smartphones, regardless of manufacturer or operating system.

These hardware vulnerabilities have been categorized into two attacks, named Meltdown (CVE-2017-5754) and Spectre (CVE-2017-5753 and CVE-2017-5715), which could allow attackers to steal sensitive data which is currently processed on the computer.
Both attacks take advantage of a feature in chips known as “speculative execution,” a technique used by most modern CPUs to optimize performance.

“In order to improve performance, many CPUs may choose to speculatively execute instructions based on assumptions that are considered likely to be true. During speculative execution, the processor is verifying these assumptions; if they are valid, then the execution continues. If they are invalid, then the execution is unwound, and the correct execution path can be started based on the actual conditions,” Project Zero says.

Therefore, it is possible for such speculative execution to have “side effects which are not restored when the CPU state is unwound and can lead to information disclosure,” which can be accessed using side-channel attacks.

The first issue, Meltdown (paper), allows attackers to read not only kernel memory but also the entire physical memory of the target machines, and therefore all secrets of other programs and the operating system.

“Meltdown is a related microarchitectural attack which exploits out-of-order execution in order to leak the target’s physical memory.”

Meltdown uses speculative execution to break the isolation between user applications and the operating system, allowing any application to access all system memory, including memory allocated for the kernel.

“Meltdown exploits a privilege escalation vulnerability specific to Intel processors, due to which speculatively executed instructions can bypass memory protection.”